Another longtime friend, Dulce Arroyo, ran across Sierra on a shopping trip two days before she left the U.S. and said traveling alone didn't appear to be a frightening prospect for Sierra. Sierra was looking forward to an exciting adventure and spent most of their conversation talking about the murals and architecture she planned to photograph.
"She was perfectly OK with taking this trip on her own," Arroyo added. "She was thrilled."
Dennis Jimenez said Sierra tried to calm any fears by emphasizing that she'd be in regular contact via video calls and text messages.
"I didn't want her to go, but she wanted to go," he said. "Turkey was a land rich in architecture and ancient history, and she was very fascinated by that."
He added that she shared her photos online and checked in frequently. "You could tell that she was happy," he said.
Grimm said Turkish police still have hours of video footage to review as they piece together Sierra's last hours. A special unit of Turkish police set up to find Sierra have an image of her at Galata Bridge, which spans Istanbul's Golden Horn waterway and where she went on her last day to take photos.
The trip also included preplanned excursions to Amsterdam and Munich.
Betzaid Jimenez said her two grandsons do not know what had happened to their mother. They only know their father went to get her after her vacation.
"We're going to talk about that when he gets back," she said.
She recalled hugging her daughter before she departed and praying together for a safe journey.
"Just the thought that I'll never be able to hug her again," she said, pausing to compose herself. "We just didn't think a tragedy like this was going to happen."
Associated Press writer Suzan Fraser in Ankara, Turkey, contributed to this report.